Processing of a workpiece such as a semiconductor wafer can be carried out using a form of electromagnetic energy, such as RF power or microwave power, for example. The power may be employed, for example, to generate a plasma, for carrying out a plasma-based process such as plasma enhanced chemical vapor deposition (PECVD) or plasma enhanced reactive ion etching (PERIE). Some processes need extremely high plasma ion densities with extremely low plasma ion energies. This is true for processes such as deposition of diamond-like carbon (DLC) films, where the time required to deposit some type of DLC films can be on the order of hours, depending upon the desired thickness and upon the plasma ion density. A higher plasma density requires higher source power and generally translates to a shorter deposition time.
A microwave source typically produces a very high plasma ion density while producing a plasma ion energy that is less than that of other sources (e.g., an inductively coupled RF plasma source or a capacitively coupled RF plasma source). For this reason, a microwave source would be ideal. However, a microwave source cannot meet the stringent uniformity required for distribution across the workpiece of deposition rate or etch rate. The minimum uniformity may correspond to a process rate variation across a 300 mm diameter workpiece of less than 1%.